The objectives of this research are to define the mechanisms responsible for the decreased serum bilirubin concentration observed with oral feedings, in order to develop improved feeding practices as an additional means of preventing and treating neonatal hyperbilirubinemia, particularly in low birth-weight infants. Glucose and saline infusions will be given by mouth, peripheral vein, and umbilical vein to premature infants to determine if an intestinal factor is necessary to facilitate serum bilirubin clearance. In addition, a sensitive biologic assay utilizing radiobilirubin will be developed in the rat for the detection of factors which affect hepatic bilirubin clearance. This assay system will be employed in experiments designed to define the mechanisms responsible for changes in serum bilirubin concentration with feeding and fasting.